SLUSE22C February   2020  – September 2025 BQ27Z561-R2

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Supply Current
    6. 5.6  Internal 1.8V LDO (REG18)
    7. 5.7  I/O (PULS, INT)
    8. 5.8  Chip Enable (CE)
    9. 5.9  Internal Temperature Sensor
    10. 5.10 NTC Thermistor Measurement Support
    11. 5.11 Coulomb Counter (CC)
    12. 5.12 Analog Digital Converter (ADC)
    13. 5.13 Internal Oscillator Specifications
    14. 5.14 Voltage Reference1 (REF1)
    15. 5.15 Voltage Reference2 (REF2)
    16. 5.16 Flash Memory
    17. 5.17 I2C I/O
    18. 5.18 I2C Timing — 100kHz
    19. 5.19 I2C Timing — 400kHz
    20. 5.20 HDQ Timing
    21. 5.21 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  BQ27Z561-R2 Processor
      2. 6.3.2  Battery Parameter Measurements
        1. 6.3.2.1 Coulomb Counter (CC)
        2. 6.3.2.2 CC Digital Filter
        3. 6.3.2.3 ADC Multiplexer
        4. 6.3.2.4 Analog-to-Digital Converter (ADC)
        5. 6.3.2.5 Internal Temperature Sensor
        6. 6.3.2.6 External Temperature Sensor Support
      3. 6.3.3  Power Supply Control
      4. 6.3.4  Bus Communication Interface
      5. 6.3.5  Low Frequency Oscillator
      6. 6.3.6  High Frequency Oscillator
      7. 6.3.7  1.8V Low Dropout Regulator
      8. 6.3.8  Internal Voltage References
      9. 6.3.9  Gas Gauging
      10. 6.3.10 Charge Control Features
      11. 6.3.11 Authentication
    4. 6.4 Device Functional Modes
      1. 6.4.1 Lifetime Logging Features
      2. 6.4.2 Configuration
        1. 6.4.2.1 Coulomb Counting
        2. 6.4.2.2 Cell Voltage Measurements
        3. 6.4.2.3 Auto Calibration
        4. 6.4.2.4 Temperature Measurements
  8. 7 Applications and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Design Requirements (Default)
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Changing Design Parameters
      3. 7.2.3 Calibration Process
      4. 7.2.4 Gauging Data Updates
        1. 7.2.4.1 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.4.1 Layout Guidelines

  • The quality of the Kelvin connections at the sense resistor is critical. Verify that the sense resistor have a temperature coefficient no greater than 50ppm to minimize current measurement drift with temperature. Choose the value of the sense resistor to correspond to the available overcurrent and short-circuit ranges of the BQ27Z561-R2 gas gauge. Select the smallest value possible to minimize the negative voltage generated on the BQ27Z561-R2 VSS node during a short circuit. This pin has an absolute minimum of –0.3V. Use parallel resistors as long as good Kelvin sensing is established. The device is designed to support a 1mΩ to 3mΩ sense resistor.
  • Directly tie the BAT_SNS to the positive connection of the battery. Verify that BAT_SNS does not share a path with the BAT pin.
  • In reference to the gas gauge circuit the following features require attention for component placement and layout: differential low-pass filter and I2C communication.
  • The BQ27Z561-R2 gas gauge uses an integrating delta-sigma ADC for current measurements. Add a 100Ω resistor from the sense resistor to the SRP and SRN inputs of the device. Place a 0.1μF filter capacitor across the SRP and SRN inputs. If required for a circuit, add 0.1µF filter capacitors for additional noise filtering for each sense input pin to ground. Place all filter components as close as possible to the device. Route the traces from the sense resistor in parallel to the filter circuit. Adding a ground plane around the filter network can provide additional noise immunity.
  • The BQ27Z561-R2 has an internal LDO that is internally compensated and does not require an external decoupling capacitor.
  • The I2C clock and data pins have integrated high-voltage ESD protection circuits; however, adding a Zener diode and series resistor provides more robust ESD performance. The I2C clock and data lines have an internal pulldown. When the gas gauge senses that both lines are low (such as during removal of the pack), the device performs auto-offset calibration and then goes into SLEEP mode to conserve power.